BMS charge / discharge controller 2S FDC-2S-2 / protection for Li-ion and Li-pol batteries


BMS controller of charge and discharge 2S FDC-2S-2, protection for Li-ion and Li-pol batteriesBoard (module) FDC-2S-2 (HX-2S-02) based on the HY2120 chip, performs the function of BMS (Battery Monitoring System) to protect 2 series-connected LI-ION / Li-pol 18650 batteries.

The module provides overcharge protection, overdischarge protection, short circuit protection. Maximum continuous discharge current up to 3A.

The module can be used in Arduino projects if 3.7 Volts is not enough, and the use of step-up DC-DC converters ( XL6009 type ) does not solve the tasks.

Specifications FDC-2S-2 (HY2120-CB)

Specifications 2S FDC-2S-2 (DS-HY2120)

  • Maximum voltage per cell when charging : 4.20-4.25v ± 0.05V;
  • Load cut-off voltage : 2.90 ± 0.08 V;
  • Charging switch-on voltage range : from 3.00 ± 0.1 V to 4.08 ± 0.05 V;
  • Fixed voltage when short circuit is detected : 1 V;
  • Overcharge protection response time : from 0.96 to 1.4 sec .;
  • Overdischarge protection response time : 110 ms;
  • Overcurrent protection response time : 7 ms;
  • Short-circuit protection response time : 250 μs;
  • Rated voltage : 7.4V (2S);
  • Charging voltage: 8.4 to 8.5V (CC / CV);
  • Working load current : 3 A;
  • Peak load current : 5 A (short-term);
  • Short circuit protection : yes;
  • Dimensions : 39 * 7 * 2 mm.
  • Working temperature : from -40 to +85 ° C;
  • Quiescent current : 5 to 9 μA;
  • Internal resistance : less than 45mΩ.

Schematic diagram of the FDC-2S-2 module

The controller wiring diagram is almost identical to the datasheet diagram. An assembly of field-effect transistors M1 and M2 (labeled 8205A) connect and disconnect the load or charger from the battery. Protective resistor R3 protects the controller from failure in charge mode. There is no current shunt on the board; in this capacity, the measurement of the drop on the assembly of transistors is used. The controller measures the voltage on the batteries, controls the field-effect transistors. The capacitor protects against voltage surges, and the resistors R1 and R2 serve as current limiters.

Schematic diagram of the FDC-2S-2 module

Near the resistor R3, you can see the place for the capacitor C3. If a small capacitor is installed in this place (select experimentally), then the microcircuit will less "see" bursts of load current, sometimes it is useful with loads that have a small static current and a large dynamic one.

Schematic diagram of the FDC-2S-2 module - protection capacitor C3

FDC-2S-2 pinout

FDC-2S-2 pinout

P-Minus load / charge
P+Plus loading / charging
B-Less battery assembly
B+Plus battery assembly
BMBattery assembly midpoint

Connection diagram FDC-2S-2

Connection diagram FDC-2S-2

P (-) to minus load / charge.
P (+) to the plus of load / charge.
B (-) to the minus of the battery assembly.
BM to the midpoint of the battery assembly.
B (+) to the plus of the battery assembly.

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